Ultimately, Time Travel is essential for Space Travel

17042011

Long-time readers may note that this blog bounces (veers?) between space-related content and time/temporal physics-related content. Today, aside from admitting that (not surprisingly) the two topics are primary passions of mine, I’ll tell you why they’re related, and intimately so.

It’s all Einstein’s fault.

After an interstellar trip, a faulty suspended animation chamber reduces an astronaut to an ancient corpse. (From Planet of the Apes; Credit: 20th Century Fox)

Put very simply, according to Relativity: When dealing with events in the universe, it is impossible to separate the distance of space from the passage of time.

This is why astrophysicists and cosmologists speak of actions in the universe occurring and affecting “space-time.” (Hence the “space-time continuum” that makes such a frequent appearance in sci-fi technobabble.)

What does this mean for us? Well, in day-to-day experience, not much more than the odd reality that the moon we see is 1 second old. Similarly, the sun we see is lagging 8 minutes behind us in time.

Why? Well, it takes the light that bounces off of the surface of the Moon 1 second to cross the 230,000-mile distance between the Earth and Moon to strike the retina of your eye, and it takes 8 minutes for the light that leaves the sun to cross the 93-million mile orbital void to get to Earth and reach your eye. As a result, we see the Moon and Sun as they appeared when the light left them, not when the light reaches us.

The same can be said of distant stars. The farther away a star is, the older it is. (Even if it’s 200,000 light years away – then you’re seeing it the way it looked 200,000 years ago.)

So, quizzically, yes – this means that universe we see is actually a horrible garble of apparent objects from intermixed times. Fortunately for us, compared to the incredible speed of light, we’re close enough (distance) to everything we need to experience, (e.g., our limbs, food, loved ones, walls, etc.,) so that this time lag is unnoticeable.

But when we start peering out into the rest of the cosmos, this distortion really matters. Many of the stars we’re studying may have already exploded… but if they exploded a few years ago, we won’t know it until light from the explosion reaches us, which could take millions of years if the star is far away.

Now, let’s take our time-distance thought exercises a step farther and ask what happens if we score the holy grail of the Search for Extraterrestrial Intelligence. What if, for the sake of argument, we receive and translate a friendly message from an incredibly advanced race of aliens? And what if, by fortuitous happenstance, they (hoping to aid other, younger life-forms) offer unlimited knowledge to any beings that can meet them on their world, face-to-face? Well, the offer doesn’t do us more than a hill of beans of good if it takes us 200 years for a multi-generational craft to get there, only to find that the benevolent race has gone extinct due to a problem with their parent star. We want to reach them as soon as we translate the message.

We want to separate the distance of space from the passage of time.

So, if we can conceptually and technologically conquer time travel, we will have in essence conquered space travel. If one can manipulate the passage of time, then the time taken to cross the distance of space with any type of propulsion system becomes an almost trivial tally – little more significant than the miles-per-gallon of a modern automobile.

Conventional propulsion systems will get us around in space for the foreseeable future, and more exotic systems will likely take us to the nearest stars. However, I believe it will be the mastery of time that will transform our race from provincial planet-hoppers to truly savvy, galaxy-trotting, cosmic-colonial game-changers.

I look at things the other way around – space travel is essential for time travel. In an hour, the solar system has moved about 100,000km around the galactic centre. So, if you go back an hour in time, you also need to be able to travel the 100,000km. In the series Terra Nova, the time jump would account for about a third of the rotation about the galactic centre. So the portal not only has to open 85 million years in the past, but also a third of the way around the galaxy. If you go back (or forward) in time, without an associated spatial movement, you’d probably appear in empty space or the middle of a sun. Looked at another way, being able to travel in time would mean that we could, de facto, travel the huge distances involved in galactic travel. Want to get to that system a third of a galactic circumference away? Just travel back (or forwards) in time 85 million years! (SF writers, you heard it here first.)

Peter – this is fantastic, as I’ve also looked at time travel the same way(!). Everything is moving, Earth about the sun, Sun about the Milky Way, Milky Way in the Local Group, etc., etc., so you could make the argument that time travel while maintaining your physical location is simply impossible (and perhaps dangerous! -Appear inside a planet or moon, and happy trails!) I actually wrote a short story involving this roughly 10 years ago, using this as a time travel limitation… But I agree with you! If time has any physical aspect, it seems that an oft ignored aspect is how the universe is moving with respect to time… It could very well be that time travel is technically possible but has very little practical application involving physical locations and may indeed relate simply to boosting the efficiency of space travel. =) Great thoughts – thanks for reading/contributing!